Rotary vane gates of the type to which the invention relates serve above all for dosaging free-flowing bulk materials and/or for introducing (charging) such bulk materials into pneumatic conveying lines when the spaces above the inlet opening and below the outlet opening are subjected to different pressures.
Various types of rotary vane gates are generally known in the art in which a compartmentalised wheel which can be driven in rotation and can be open or closed on its end faces is received in a housing which is largely closed--up to the inlet opening and outlet opening. In the case of rotary vane gates, or the compartments which are formed therein, which are open on the end faces, during the rotary movement of the wheel and thus on the way from the inlet to the outlet opening the bulk material comes into contact with the inner faces of the housing cover on the end faces, so that in the case of abrasive bulk material a considerable wear by abrasion is caused. After a relatively short time this wear proves particularly disadvantageous in the case of rotary vane gates which are subjected to comparatively high pressure differences and/or in which it is necessary to ensure a relatively high resistance to pressure shocks or safety against penetration of flames (because of bulk materials, e.g. coal dust, which have a tendency to explode).
A known rotary gate is disclosed in DE-B-24 19 841 as one in which the wheel and thus also the compartments formed therein is delimited by end faces or end plates. In this case a space is formed at each end between the end face and the neighbouring housing cover, and continuously pressurised clean air is introduced by way of a branch line as scavenging air into this space, this air being intended to flow on the one hand through the gaps between the circumference of the wheel and the housing in the direction of the inlet and on the other hand through the space and an outlet gap provided in the lower region into the Mate outlet. In this way the occurrence of leakages and the penetration of material for conveying into the said spaces should be prevented as thoroughly as possible on the other hand, however, the spaces should be continuously scavenged so that any dust penetrating into them can be drawn off into the gate outlet.
Thus in the known construction described above special line connections together with connecting arrangement and pressure monitoring and adjusting instruments are necessary at corresponding expense for the delivery of scavenging air into the two spaces. Moreover, however, it has also been shown in the art that in the case of many bulk materials it is not always possible entirely to prevent quantities of dust from becoming attached on the inner faces of the spaces which can gradually build up into such thick layers that because of the end faces of the wheel rotating relative to the fixed housing covers not only does an undesirable abrasion take place but the necessary rotary driving moment for the wheel increases in such a way that the wheel locks in the housing after a certain time.
The object of the invention, therefore, is to avoid the described disadvantages of the known constructions and to provide a rotary vane gate which has a relatively simple construction and is distinguished by a far-reaching avoidance of wear by abrasion on the housing covers as well as by an extremely reliable operation. When used for dosaging and/or charging of bulk materials which tend to explode (e.g. coal dust) this gate should also be constructed so as to be as resistant to pressure shocks and as safe against penetration of flames as possible.